Sickle cell disease and the kidney

Prevalence and Factors Associated with Acute Kidney Injury in Sub-Saharan African Adults: A Review of the Current Literature

Acute kidney injury (AKI) is a complex condition that can occur in both community and hospital settings and has many aetiologies. These aetiologies may be infectious, toxic, surgical, or related to the different management methods. Although it is a major public health problem worldwide, it must be emphasised that both its incidence and mortality rate appear to be very high in sub-Saharan African (SSA) countries compared to developed countries. The profile of AKI is very different from that of more developed countries. There are no reliable statistics on the incidence of AKI in SSA. Infections (malaria, HIV, diarrhoeal, and other diseases), nephrotoxins, and obstetric and surgical complications are the main aetiologies in Africa. The management of AKI is costly and associated with high rates of prolonged hospitalisation and in-hospital mortality.

Sickle Cell Nephropathy and Associated Factors among Asymptomatic Children with Sickle Cell Anaemia

BACKGROUND

Sickle cell nephropathy (SCN) is a serious complication of sickle cell anaemia (SCA) with asymptomatic onset in childhood and possible progression to chronic kidney disease (CKD). In Southeast Nigeria, few studies have evaluated renal function in paediatric SCA patients for early detection of renal impairment and early intervention to reduce morbidity and mortality. Therefore, this study evaluated the renal function of paediatric SCA patients in a steady state based on glomerular filtration rate and urinalysis findings (proteinuria and haematuria).

METHODS

A cross-sectional study of consecutively recruited sixty haemoglobin SS (HbSS) children in a steady state and sixty age- and sex-matched haemoglobin AA (HbAA) controls aged 2-18 years was done. Renal function of HbSS subjects was evaluated using estimated glomerular filtration rate (eGFR) which was compared with healthy HbAA subjects. The prevalence of significant proteinuria and haematuria, its association with eGFR, and the effect of past sickle cell crisis (in the preceding 24 months) on renal function were also evaluated.

RESULTS

Mean eGFR was significantly higher in HbSS subjects than in the HbAA subjects (p = 0.001) and decreased with age. Significant proteinuria and haematuria were more prevalent in the HbSS group (3.4% and 6.7%, respectively) compared to the HbAA subjects (0% and 0%, respectively) (p = 0.496 and 0.119, respectively). No significant association was observed between eGFR and proteinuria (p = 1.000) or haematuria (p = 1.000). There was a positive correlation between eGFR and frequency of past painful crisis that required hospitalization (r = 0.138, p = 0.295) and between eGFR and frequency of blood transfusion (r = 0.679, p ≤ 0.001).

CONCLUSIONS

Asymptomatic paediatric HbSS (SCA) patients had higher mean eGFR indicating an increased risk of nephropathy. There was no association between eGFR and proteinuria or haematuria. Frequent sickle cell crises especially one requiring transfusion were positively correlated with hyperfiltration.

Kidney Disease among Patients with Sickle Cell Disease, Hemoglobin SS and SC

BACKGROUND AND OBJECTIVES

Sickle cell disease (SCD) is an inherited anemia that afflicts millions worldwide. Kidney disease is a major contributor to its morbidity and mortality. We examined contemporary and historical SCD populations to understand how renal disease behaved in hemoglobin SS (HbSS) compared with HbSC.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Kidney function was examined in the multicentered Treatment of Pulmonary Hypertension and Sickle Cell Disease with Sildenafil Therapy (Walk-PHaSST) Trial (HbSS=463; HbSC=127; years 2007-2009) and historical comparator populations from the Cooperative Study of Sickle Cell Disease (CSSCD; HbSS=708) and the Multicenter Study of Hydroxyurea in Sickle Cell Disease (MSH; HbSS=299).

RESULTS

In adults with SCD, eGFR was lower among older individuals: -1.78 ml/min per 1.73 m(2) per year of age (95% confidence interval [95% CI], -2.06 to -1.50; Walk-PHaSST Trial), -1.75 ml/min per 1.73 m(2) per year of age (95% CI, -2.05 to -1.44; MSH), and -1.69 ml/min per 1.73 m(2) per year of age (95% CI, -2.00 to -1.38; CSSCD) in HbSS compared with -1.09 ml/min per 1.73 m(2) per year of age (95% CI, -1.39 to -0.75) in HbSC (Walk-PHaSST Trial). Macroalbuminuria was seen in 20% of participants with SCD (HbSS or HbSC; P=0.45; Walk-PHaSST Trial), but microalbuminuria was more prevalent in HbSS (44% versus 23% in HbSC; P<0.002). In the Walk-PHaSST Trial, albuminuria was associated with hemolysis (higher lactate dehydrogenase, P<0.001; higher absolute reticulocyte count, P<0.02; and lower Hb, P=0.07) and elevated systolic BP (P<0.001) in HbSS. One half of all participants with HbSS (20 of 39) versus one fifth without (41 of 228) elevated tricuspid regurgitant jet velocity (≥3 m/s; adverse prognostic indicator in SCD) had macroalbuminuria (P<0.001). In the CSSCD, overt proteinuria, detected (less sensitively) by urine dipstick, associated with higher 3-year mortality (odds ratio, 2.48; 95% CI, 1.07 to 5.77). Serum bicarbonate was lower in HbSS (23.8 versus 24.8 mEq/dl in HbSC; P<0.05) and associated with reticulocytopenic anemia and decreased renal function.

CONCLUSIONS

In SCD, albuminuria or proteinuria was highly prevalent, in HbSS more than in HbSC. Proteinuria associated with mortality in HbSS. Older individuals had a lower than expected eGFR, and this was more prominent in HbSS. Current management does not routinely address renal complications in SCD, which could plausibly reduce morbidity and mortality.

Correction of murine hemoglobinopathies by prenatal tolerance induction and postnatal nonmyeloablative allogeneic BM transplants

Sickle cell disease (SCD) and thalassemias (Thal) are common congenital disorders, which can be diagnosed early in gestation and result in significant morbidity and mortality. Hematopoietic stem cell transplantation, the only curative therapy for SCD and Thal, is limited by the absence of matched donors and treatment-related toxicities. In utero hematopoietic stem cell transplantation (IUHCT) is a novel nonmyeloablative transplant approach that takes advantage of the immunologic immaturity and normal developmental properties of the fetus to achieve mixed allogeneic chimerism and donor-specific tolerance (DST). We hypothesized that a combined strategy of IUHCT to induce DST, followed by postnatal nonmyeloablative same donor "booster" bone marrow (BM) transplants in murine models of SCD and Thal would result in high levels of allogeneic engraftment and donor hemoglobin (Hb) expression with subsequent phenotypic correction of SCD and Thal. Our results show that: (1) IUHCT is associated with DST and low levels of allogeneic engraftment in the murine SCD and Thal models; (2) low-level chimerism following IUHCT can be enhanced to high-level chimerism and near complete Hb replacement with normal donor Hb with this postnatal "boosting" strategy; and (3) high-level chimerism following IUHCT and postnatal "boosting" results in phenotypic correction in the murine Thal and SCD models. This study supports the potential of IUHCT, combined with a postnatal nonmyelablative "boosting" strategy, to cure Thal and SCD without the toxic conditioning currently required for postnatal transplant regimens while expanding the eligible transplant patient population due to the lack of a restricted donor pool.

Degrees of kidney disease in nigerian adults with sickle-cell disease

OBJECTIVE

To study degrees of chronic kidney disease (CKD) using creatinine clearance in adult Nigerian patients with sickle-cell disease (SCD).

METHODS

One hundred SCD patients, made up of 79 HbSS (homozygous haemoglobin S) patients and 21 HbSC (heterozygous haemoglobins S and C) patients, were investigated prospectively, along with 50 normal controls. Their sociodemographic data, weight and drug history were documented. Each participant underwent dipstick urinalysis, and creatinine clearance was calculated following a 24-hour urine collection and serum creatinine measurement. They were categorized into stages of CKD based on the creatinine clearance.

RESULTS

Of the 79 HbSS patients, 14 (18%), 28 (35%), 33 (42%) and 4 (5%) had stage 1, 2, 3 and 4 CKD, respectively. In the HbSC group, 3 (14%), 9 (43%) and 9 (43%) patients had stage 1, 2 and 3 CKD, respectively. Proteinuria was noted in 16 (20%) HbSS patients but not in any of the HbSC patients. Of the subjects aged ≤24 years (n = 49), 9 (18%), 18 (37%), 21 (43%) and 1 (2%) had stage 1, 2, 3 and 4 CKD, respectively. Of those aged >24 years (n = 51), 8 (16%), 19 (37%), 21 (41%) and 3 (6%) had stage 1, 2, 3 and 4 CKD, respectively. None of the subjects had stage 5 CKD.

CONCLUSION

In this study, the adult subjects with SCD had various degrees of CKD. Adequate follow-up and active intervention are advocated to delay the onset of end-stage nephropathy.

Current sickle cell disease management practices in Nigeria

BACKGROUND

Although Nigeria has the highest burden of sickle cell disease (SCD) worldwide, there is still variable and poor utilisation of standard-of-care practices for SCD patients in the country.

METHODS

This was a questionnaire survey of doctors in some dedicated SCD clinics in Nigeria in order to document the facilities available and common management practices.

RESULTS

There were responses from 18 clinics based in 11 institutions. The number of patients being followed in each centre ranged from 15 to approximately 11 000. All clinics provided malaria prophylaxis and folic acid routinely to their patients. Only eight clinics prescribe penicillin prophylaxis. Eight prescribe hydroxyurea to patients who can afford it when indicated. All of the centres except three have electronic cell counters, but all had access to haemoglobin electrophoresis. Three had high-performance liquid chromatography machines installed but none was being routinely used. One institution had a functioning molecular biology laboratory. There is no official newborn screening programme in the country. All had access to microbiology and chemistry laboratories. Nine institutions had CT, six had MRI and three had transcranial Doppler facilities.

CONCLUSION

The care available for SCD in Nigeria is still suboptimal and there is an urgent need for concerted effort to tackle the problem, but to make a significant impact on the burden of the disease would require more focus at the primary care level. Some steps to achieving this are outlined.

Effect of sickle cell crises on glomerular filtration rate in children with sickle cell disease in Ilorin, Nigeria

Children with sickle cell disease (SCD) are plagued with incessant crises. There are few studies on the effect of sickle cell crises on renal function as determined by the glomerular filtration rate (GFR). This study was done to assess the effect of sickle cell crises on GFR during crises and after recovery into the steady state. GFR was assessed using the formula derived by Schwartz et al., for consecutive SCD patients aged between 3 and 18 years who came in crises and after recovery into the steady state. A total of 81 patients with a mean age of 9.95 ± 4.15 years in 81 episodes of crises met the inclusion criteria. Majority of the children (47) had vasooclusive crises, 19 had hyperhaemolytic crises, and 15 had features of both vasooclusive and hyperhaemolytic crises. The means value of GFR in ml/min/1.73 m(2) rose from 81.09 ± 22.92 to 116.24 ± 22.11 subsequent to recovery from vasooclusive crises into the steady state, from 77.45 ± 18.48 to 99.54 ± 17.71 following recovery from hyperhaemolytic crises into the steady state and from 90.95 ± 17.53 to 114.01 ± 22.44 following recovery from crises with features of both vasooclusive and hyperhaemolytic crises with corresponding significant P values of 0.000, 0.001, and 0.004 respectively. The reduced GFR observed during vasooclusive and hyperhaemolytic crises improved significantly following recovery into the steady state.

[Pathological peculiarities of chronic kidney disease in patient from sub-Saharan Africa. Review of data from the Democratic Republic of the Congo]

Chronic kidney disease (CKD) is a major global public health problem. But kidney involvement is more common and appears more severe in Africa than in developed countries. The likely causes of end stage renal disease (ESRD) or CKD stage 3 and above in developed countries are diabetes, hypertension and less frequently glomerular diseases. In contrast, in decreasing order in Africa are glomerulopathies, hypertension and diabetes. The reasons for this preponderance of glomerular diseases are not fully known but may be linked to the persistence or reemergence of tropical diseases. This study reviews the kidney involvements more associated with common tropical diseases including HIV/AIDS. The most common HIV/AIDS lesion is a specific focal and segmental glomerulosclerosis (FSGS) termed HIV-associated nephropathy (HIV-AN). Renal complications of tropical parasites are heterogenous. Various glomerulopathies like FSGS occur during various filariasis infections. Schistosoma mansoni is responsible for membranoproliferative glomerulonephritis and amyloidosis. Human African trypanosomiasis is associated with cryoglobulinemic membranoproliferative glomerulonephritis. The Plasmodium malariae is mainly responsible for membranoproliferative glomerulonephritis. Acute patterns (acute tubular necrosis or acute postinfectious glomerulonephritis) are observed during Plasmodium falciparum infection. Several other viral, bacterial or mycobacterial infections like leprosy and tuberculosis still prevalent in Africa can also affect the kidney. Sickle cell disease is responsible for a variety of renal injuries. In conclusion, kidney lesions linked to tropical diseases partly explain the peculiar pattern of CKD of the black race and play a significant role in the current outbreak of the CKD in Subsaharan Africa.

Glomerular lesions in patients with sickle cell disease

Sickle cell disease (SCD) is an increasing cause of chronic kidney disease, but the spectrum of glomerular lesions and their underlying mechanisms remain poorly described. We reviewed 18 renal biopsies from patients with SCD and glomerular involvement and studied the expression of hypoxic markers in the biopsy specimens. Four histopathologic variants were distinguished: focal segmental glomerulosclerosis (FSGS) (39%), membranoproliferative glomerulonephritis (28%), thrombotic microangiopathy glomerulopathy (17%), and specific sickle cell disease glomerulopathy (17%). Chronic organ damage and history of acute chest syndrome were associated with the occurrence of SCD glomerulopathy. All patients exhibited macroalbuminuria but only 6 patients displayed impaired renal function. SCD was not associated with a specific FSGS histologic variant. Long-term follow-up analysis revealed that 50% of patients exhibited chronic kidney disease. Regardless of the histologic variants, immunohistochemistry did not reveal a specific induction of hypoxic markers (inducible nitric oxide synthase [iNOS], nitrotyrosine, hypoxia-inducible factor [HIF]-1 alpha) at the time of renal biopsy. This large study shows that a wide spectrum of glomerular lesions is associated with SCD. Whatever lesions are observed, the renal prognosis is poor, and early renoprotective treatment is necessary. Hypoxic state does not seem to play a key role in the progression of glomerular lesions, but its potential role at an early stage of glomerular injury requires further investigation.

Thrombosis after kidney transplantation

The diagnosis of deep vein thrombosis (DVT) is unusual in patients with sickle cell disease (SCD). Despite the incidence of cerebral thrombosis in SCD patients due to vasooclusion, thrombotic manifestations in peripheral vessels are rare. Patients with homozygous SCD present a variety of renal abnormalities as a result of sickle crisis. In this group of patients, kidney transplantation has been performed in the renal endstage patients; with graft survival rates similar to that of the general transplant population at 1 year. However, patients with SCD experience an augmentation in the frequency of painful crises in the first year after transplantation, which has been attributed to concurrent elevations in hematocrit and plasma viscosity. Despite etiology, renal transplant patients are at increased risk for the development of thromboembolic events such as deep vein thrombosis and renovascular thrombosis after allograft procedure. These events can be due to a prothrombotic state generated by the use of immunosuppressive agents. Although other factors such as acquired or inherited disorders of the clotting system may increase the risk of thrombosis. Here, we report a case of a renal transplant patient with sickle cell disease who presented recurrent episodes of DVT and increase painful sickle episodes after kidney transplantation.

Correction of murine sickle cell disease using gamma-globin lentiviral vectors to mediate high-level expression of fetal hemoglobin

Increased levels of red cell fetal hemogloblin, whether due to hereditary persistence of expression or from induction with hydroxyurea therapy, effectively ameliorate sickle cell disease (SCD). Therefore, we developed erythroid-specific, gamma-globin lentiviral vectors for hematopoietic stem cell (HSC)-targeted gene therapy with the goal of permanently increasing fetal hemoglobin (HbF) production in sickle red cells. We evaluated two different gamma-globin lentiviral vectors for therapeutic efficacy in the BERK sickle cell mouse model. The first vector, V5, contained the gamma-globin gene driven by 3.1 kb of beta-globin regulatory sequences and a 130-bp beta-globin promoter. The second vector, V5m3, was identical except that the gamma-globin 3'-untranslated region (3'-UTR) was replaced with the beta-globin 3'-UTR. Adult erythroid cells have beta-globin mRNA 3'-UTR-binding proteins that enhance beta-globin mRNA stability and we postulated this design might enhance gamma-globin expression. Stem cell gene transfer was efficient and nearly all red cells in transplanted mice expressed human gamma-globin. Both vectors demonstrated efficacy in disease correction, with the V5m3 vector producing a higher level of gamma-globin mRNA which was associated with high-level correction of anemia and secondary organ pathology. These data support the rationale for a gene therapy approach to SCD by permanently enhancing HbF using a gamma-globin lentiviral vector.

Sickle cell disease complicated by post-streptococcal glomerulonephritis, cerebral hemorrhage and reversible posterior leucoencephalopathy syndrome

A patient with homozygous hemoglobin SS disease presented with an intracerebral hemorrhage complicating reversible posterior leucoencephalopathy syndrome (RPLS), secondary to hypertension associated with acute post-streptococcal glomerulonephritis (APSGN). Distinguishing potentially reversible causes of central nervous system events from primary cerebral infarction or hemorrhage in patients with sickle cell disease is important because the management and prognosis of these complications is very different. Similarly, because of the difference in prognosis between APSGN and other forms of sickle cell nephropathy, it is also important to differentiate these conditions.

Estimated glomerular filtration rate in sickle cell anemia is associated with polymorphisms of bone morphogenetic protein receptor 1B

Renal disease is common in sickle cell anemia. In this exploratory work, we used data from a longitudinal study of the natural history of sickle cell disease to examine the hypothesis that polymorphisms (SNPs) in selected candidate genes are associated with glomerular filtration rate (GFR). DNA samples and clinical and laboratory data were available for 1,140 patients with sickle cell anemia. GFR was estimated using the Cockcroft-Gault and Schwartz formulas for adults and children, respectively. We examined approximately 175 haplotype tagging (ht) SNPs in about 70 genes of the TGFbeta/BMP pathway for their association with GFR using linear regression. Four SNPs in BMPR1B, a bone morphogenetic protein (BMP) receptor gene, yielded statistically significant associations (P values ranging from 0.015 to 0.046). Three haplotypes in this gene were also associated with GFR. The TGF-beta/BMP pathway has been associated with the development of diabetic nephropathy, which has some features in common with sickle cell nephropathy. Our results suggest that, as with other subphenotypes of sickle cell disease, renal function may be genetically modulated.

Predicting initiation and progression of chronic kidney disease: Developing renal risk scores

Epidemiological studies have raised awareness of the problem of undiagnosed chronic kidney disease (CKD) and suggest that early identification and treatment will reduce the global burden of patients requiring dialysis. This has highlighted the twin problems of how to identify subjects for screening and target intervention to those with CKD most likely to progress to end-stage renal disease. Prospective studies have identified risk factors for CKD in the general population as well as risk factors for progression in patients with established CKD. Risk factors may thus be divided into initiating factors and perpetuating factors, with some overlap between the groups. In this paper, we review current data regarding CKD risk factors and illustrate how each may impact upon the mechanisms underlying CKD progression to accelerate loss of renal function. We propose that these risk factors should be used as a basis for developing a renal risk score, analogous to the Framingham risk score for ischemic heart disease, which will allow accurate determination of renal risk in the general population and among CKD patients.

Early blood transfusions protect against microalbuminuria in children with sickle cell disease

BACKGROUND

Microalbuminuria (MA) is an early indicator for glomerulopathy in sickle cell disease (SCD).

PROCEDURE

We reviewed the medical records of asymptomatic patients ages 4-20 with sickle hemoglobinopathies, who were screened for MA in order to find out its prevalence and risk factors.

RESULTS

Nineteen of 120 (15.8%) screened patients had MA detected by spot urine (mean albumin absolute value 6.95 +/- 0.56 mg/dl) and abnormal albumin to creatinine ratios (79.8 +/- 0.62 mg/g creatinine). Twenty four-hour urine collections confirmed 57% of MA cases by spot urine. There was no difference in hyperfiltration between positive and negative patients. From the MA-positive patients, 15 had SS (16.8% of SS group) and 4 had SC (18% of SC group). Nineteen percent of children 10 years of age or older had MA, as compared to 8% of the younger children (P = 0.018), demonstrating that increasing age is a risk factor for MA. There was a positive correlation between MA and acute chest syndrome. Young age at start of chronic transfusions was inversely related to MA and therefore renoprotective (P = 0.03). We did not see a protective effect in the group of patients taking hydroxyurea for a relatively short time, mean age at start of treatment 12 +/- 5 years; however the sample was small.

CONCLUSIONS

We conclude that: (1) children with sickle cell hemoglobinopathies 10 years or older should be screened for MA and (2) chronic transfusions starting at an early age may be renoprotective.

[Enuresis in children with sickle cell disease]

POPULATIONS AND METHODS

In order to analyze epidemiological and clinical characteristics of enuresis in children with sickle cell disease, and identify risk and aetiological factors, 987 subjects (aged 5-20 years) took part in a cross-sectional study. These children were divided into two groups: group 1 consisted of 456 homozygous children with sickle cell disease (haemoglobin SS), while group 2 consisted of 531 normal children. These groups were paired according to age and sex.

RESULTS

The prevalence of enuresis was 50.9% in group 1 and 16.4% in group 2, and was significantly higher (P < 0.05) in the girls. The frequency decreased significantly between the ages of 5-20. At age 16, frequency of enuretic children with sickle cell disease remained statistically greater (15.9% vs. 8.0%). The frequency of wet nights was higher (P < 0.05) in group 1. In addition, anaemia crisis and painful crisis were related to prevalence of enuresis. There was a significant (P < 0.01) negative correlation between haemoglobin F percentage and prevalence of enuresis.

CONCLUSION

Enuresis is frequent in children with sickle cell disease and its intensity is linked to severity of disease.